Atopic dermatitis occurs as an allergic reaction in the skin, the main mechanism is the production of IgE antibodies against specific allergens. The antibodies are coated to mast cells, a type of cell present in epithelial tissues. When the allergen comes into contact with IgE, the mast cell degranulates and releases histamine and a number of other compounds that stimulate a local inflammatory reaction. As the skin and the nasal and conjunctival epithelia are most prone to come into contact with allergens, this is also the place where allergic symptoms develop most commonly.
Atopic eczema is caused by general systemic allergic reactions, as opposed to contact with an irritant. It is very common in people with related allergic conditions, including asthma or chronic hay fever.
It is presumed that predisposed individuals develop Type 1 allergy against a number of very abundant allergens, such as the house dust mite excrement and grass pollen. All allergens are protein-based.
Symptoms and clinical manifestations
The clinical picture is that of eczema. Primary lesions (the disease appearance at the very start) may include papules, erythematous macules, and vesicles, which can coalesce to form patches and plaques. In severe eczema, secondary lesions (the disease appearance later on) from infection or excoriation, marked by weeping and crusting, may predominate. Long-standing dermatitis is often dry and is characterized by thickened, scaling skin (lichenification).
Atopic dermatitis is often associated with a personal and/or family history of allergic diseases such as rhinitis, urticaria, and asthma, with positive wheal-and-flare skin reactions to intradermal injection of extracts of airborne allergens, with increased levels of IgE in the serum, and/or with a positive response to provocation tests involving the inhalation of specific allergen.
It is important to identify any possible contact allergens. Treatment of coexistent infection, and application of topical glucocorticoids (preferably combined with a topical antibiotic) are usually sufficient.
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